Do HIV drugs really mean you aren’t infectious?

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The
impact of HIV treatment on infectiousness has been a hotly debated topic in
recent years. It’s now nearly three years since several Swiss doctors upset the
HIV prevention applecart by writing a paper that said that, under carefully stipulated
conditions - viral load under 50
copies/ml for at least six months, no sexually transmitted infections, 100%
adherence to HIV therapy - a person on antiretroviral drugs was essentially
unable to transmit HIV sexually.1

Far from
settling the issue, the ‘Swiss statement’ stirred up huge amounts of argument
in the HIV prevention community. Everyone agrees people on successful HIV
therapy are probably quite a lot less infectious than people not on treatment.
But are they uninfectious enough to mean it’s worth taking the risk of not
using condoms? The past month has seen the publication of several new studies which,
unfortunately, muddy the waters on this particular issue rather than clarify
them.

The Swiss
doctors based their findings on research involving heterosexual couples that
showed there were no HIV transmissions when viral load was below a certain
level. This is because HIV treatment reduces the amount of virus in body
fluids, including genital fluids.

But there
are concerns that even people who have an undetectable viral load in their
blood may not always have an undetectable viral load in their genital fluids. A
number of studies have shown this in men – and an even higher proportion in
women.

Treatment
reduced viral load in the blood and genital fluids. The researchers also found
that the level of viral load in the blood tended to predict viral load in these
genital fluids.

At the
end of the study, after taking treatment for six months, 69 women had an
undetectable viral load in their blood, but viral load was still detectable in
the cervical fluids of 10% of these women and in the vaginal secretions of 32%.

So far,
this is what other studies have found. But there’s never really been an
explanation as to why some women maintained a viral load in their genitals when
they haven’t got one in their veins. One theory was that it was to do with
low-level, asymptomatic infection with sexually transmitted viruses like HSV-2
(herpes) and the genital wart virus HPV (human papillomavirus). Others thought
it was just constitutional – some people were just, to use a delightful phrase
coined by the researchers, “super-shedders” when it came to producing HIV.

This
study found a much simpler, and more easily fixed, explanation: the single most
important factor associated with a detectable viral load in genital fluids was
poor adherence to treatment. When we say ‘poor’, it was actually very good: on
average, the women forgot only one in a hundred doses. Nonetheless, the women
who didn’t do quite so well on adherence were considerably more likely to have
a detectable viral load in their genital fluids than ones whose adherence was
perfect.

On the
one hand, this means that when the Swiss statement specified 100% adherence to
ensure non-infectiousness it really meant it, which may be a tall order for
anyone. On the other hand, it does mean there may be a simple and relatively fixable
explanation as to why some people are more infectious than others.

Real-world evidence

The
evidence about the impact of treatment on the risk of HIV transmission largely
comes from big randomised controlled studies. For instance, a study in Africa
last year found that the chances of HIV being passed on between partners was
reduced by 92% - better than the average reduction due to attempted consistent
condom use – if the HIV-positive partner was on treatment.3 That’s a big treatment bonus.

People
enrolled in these trials generally receive a lot of support and good medical
care. Often this is at a higher level than is available from routine medical
services.

However,
‘real-world’ evidence from the US
and Canada
has suggested that high rates of treatment within the community may be starting
to help prevent new infections.

However, Chinese
researchers also looked at this question recently, and found a result that was
completely out of line with this.4
Their research involved 1927 couples where one partner was HIV-positive and the
other HIV-negative. These couples were monitored for approximately three years.

The
transmission rate in couples where the HIV-positive partner was taking
treatment was 5%, compared to a transmission rate of 3% in the other couples. That
makes it look as if taking treatment was worse in terms of infectiousness than
not taking it, but in statistical terms the 2% difference is within the margin
of error, and it essentially means the risk was the same, regardless of
treatment. Nonetheless, this is a drastically different result from the African
study.

In an
editorial that accompanied the study, Myron Cohen, a senior US HIV doctor, said
the results of this study should cause those who support the wider use of HIV
treatment as a way of controlling the spread of the virus to “pause”.5

But why
was the result so wildly out of line? In their own paper, the researchers note
that people on treatment who did not switch their regimens were much more
likely – nearly three times as likely – to transmit HIV than people who had
switched their drug regimens.

Why might
this be a clue? Well, the researchers did not provide any information on the
viral load of the individuals who transmitted HIV to their partners, about
whether they had drug resistance, or about measures to support adherence.

However,
they also noted that a previous study of drug resistance in Henan province found
that only one third of people with HIV were adherent to their treatment after
six months of therapy, and that by this time (from an original figure of 14%
with drug-resistant HIV), no less than 63% had drug resistance.6

We can’t
tell if the same situation applied in this study. But if adherence is poor and people
in this region do have high rates of resistance, perhaps due to a lack of
support or treatment education, then failing to switch therapies might mean
they are much more likely to have drug-resistant HIV – which they then transmit
to their partner – than they are if they move to a new therapy.

Until we
get more information, we won’t know if that’s the explanation and, as Dr Cohen says,
this gives us pause for thought. However, what this study may be showing us is
simply that suboptimal treatment regimens and levels of support produce
prevention failure as well as treatment failure.

HIV transmission risk in gay couples

Most of
the evidence on the impact of treatment on infectiousness comes from
heterosexuals.

But now
researchers have attempted to calculate the HIV transmission risk in stable gay
couples where one partner is HIV-negative and the other HIV-positive and taking
treatment.7

Using
condoms all the time provided the most protection against HIV. The researchers
calculated that there was a 1% risk of transmission in these circumstances.

Having
unprotected sex within six months of the most recent undetectable viral load,
but using condoms at all other times, was associated with a 3% risk of
transmission. Never using condoms was associated with a 22% risk of
transmission.

The
researchers say the key message is that consistent condom use is the best way
of protecting one’s partner. They also say that the most crucial time to use
condoms is when more than three months have gone by since the last undetectable
viral load result.

So there
you are. HIV treatment will reduce
your viral load if it’s successful, and if that happens, you are probably less
infectious. But what these studies seem to suggest collectively is that there
are an awful lot of ifs and buts to add to that statement and it might not be
time to throw away the condoms quite yet.

Issue 201: November 2010

This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.

NAM’s information is intended to support, rather than replace, consultation with a healthcare professional. Talk to your doctor or another member of your healthcare team for advice tailored to your situation.

The Community Consensus Statement is a joint initiative of AVAC, EATG, MSMGF, GNP+, HIV i-Base, the International HIV/AIDS Alliance, ITPC and NAM/aidsmap

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This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends
checking whether this is the most current information when making decisions that may affect your health.

NAM’s information is intended to support, rather than replace, consultation with a healthcare professional. Talk to your doctor or another member
of your healthcare team for advice tailored to your situation.